This invention relates to a device for joining adjacent frame members, such as picture frame members, where the ends to be joined are bevelled at matched angles to form a mitrejoint.
A mitre-joint is formed when two frame members having the same cross-sectional shape are joined at their ends. Normally the ends to be joined are bevelled at equal angles. This type of joint is used in the aluminium security door construction industry, when, for example, upright members are joined to the top and bottom members to form a rectangular frame surrounding the security grille. Mitre joints are also extensively used in the carpentry trade for framing and end jointing of timber trim. The joining of such frame members must result in a strong and stable joint, and it is desirable that the join line be as unobtrusive and as invisible as possible.
Mitre-joints are also used to join the four side pieces of a picture frame, where it is important that the joints do not open or work loose and the joining means is to be kept hidden from view.
Of course many different types of materials for various applications are so joined, for example, wooden and plastic picture frame material, wooden architraves, aluminium and structural steel frame work.
The making of a correct mitre-joint requires a deal of skill which ensures that the bevel of each piece is complementary with the abutting piece and that an appropriate joining means is chosen and applied correctly so that the join line has a close fit and is therefore barely visible. It takes time and expertise to make each join and not always is the correct combination of material and method used. Problems commonly occur when the joining means chosen is inappropriate for the final use of the joint, alternatively the tightening of the joint fixing means actually opens the joint rather than closes it resulting in the visual appearance of the joint being less than satisfactory.
Sometimes the joining means causes the pieces being joined to twist about their longitudinal axis even though they are positioned correctly before being fixed with the joining means. This can be caused by the use of joining means such as screws or nails, which are difficult to use without causing relative movement of the frame members.
The making of a frame is therefore considered a skilled task. There is however a need for a simpler joining system where an unskilled person can easily assemble such frames. It is an object of this invention to provide a joining device which allows easy and stable construction of frame members using mitre-joints. The advantages of such a device would ensure ease and speed of construction resulting in a consistent quality of framing joint which are capable of being easily assembled.